Researchers create microscopic muscle with 1000x human strength

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You’ve probably heard plenty about revolutionary materials like graphene and carbon nanotubes, but what about vanadium dioxide? If that doesn’t ring a bell right now, it might soon. A team of researchers at the Department of Energy’s Lawrence Berkeley National Laboratory has used this peculiar metal to fashion a nano-scale muscle with more than 1000 times the strength of a human muscle of the same scale.

Vanadium dioxide is of interest to researchers for its remarkable thermoelectric properties. It is an insulator at low temperatures, but flips abruptly to being a conductor at 67 degrees celsius. That could be big for the design of electronic circuits, but vanadium dioxide can also undergo structural changes in response to temperature — it contracts along one dimension while expanding along the other two. It is this property that was used to create the microscopic muscle at Lawrence Berkeley National Laboratory.

The micro-muscle is a coil composed of vanadium dioxide just a few hundred micrometers long. When it is heated, the conformational change causes the helical structure to expand. This acts like a tiny catapult that can launch objects away at phenomenal speeds. The coil is able to toss a microparticle 50 times more massive than itself about five coil lengths away in only 60 milliseconds. That makes it by far the most energy-dense microscopic motor ever devised.

The vanadium dioxide coil can also be used as a proximity sensor that reacts to the presence of an object by pushing it away in a similar fashion to the catapult. The researchers likened this to a neuron-driven response in a living organism.

The team found that the vanadium dioxide micro-muscles show amazing resilience — after more than one million rotations at up to 200,000 rpm, they showed no loss of function. This material could end up powering a new generation of microscopic motors that simulate organic neuromuscular systems on the small scale.